Visual, continuous and simultaneous measurement of solution ammonia and hydrogen ion concentration

ABSTRACT

Particular aspects provide novel devices and methods for accurately measuring total ammonia (NH 3  plus NH 4   + ) in a solution (e.g., freshwater and saltwater) by spatially proximate, simultaneous and continuous quantitative measurement of solution pH and ammonia. The devices overcome prior art inaccuracies relating to non-homogeneous sampling, and to spatial, temporal and thermal sampling discontinuities. Particular embodiments provide a combination pH and ammonia measuring device, comprising: a submersible member; a submersible non-bleeding ammonia-sensing portion attached to the submersible member and suitable to provide for a continuous visual indicator of solution ammonia concentration; a submersible non-bleeding pH-sensing portion attached to the submersible member and suitable to provide for a continuous visual indicator of solution pH; visual ammonia and pH indicator comparison means suitable for comparative quantitative determination of solution ammonia concentration and pH. Additional aspects provide novel ultra-sensitive devices and methods using same for measuring ammonia in air or solution.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/696,695, filed 4 Apr. 2007 and entitled “VISUAL, CONTINUOUS ANDSIMULTANEOUS MEASUREMENT OF SOLUTION AMMONIA AND HYDROGEN IONCONCENTRATION,” which claims the benefit of priority to U.S. ProvisionalPatent Application Ser. No. 60/788,983, filed 4 Apr. 2006 of same title,which are incorporated by incorporated by reference herein in theentirety.

FIELD OF THE INVENTION

Aspects of the present invention relate generally to means for measuringthe status of an air or aqueous environment (e.g., freshwater andsaltwater), and more particularly to novel methods and devices foraccurately measuring total ammonia (NH₃ plus NH₄ ⁺) in a solution byproximate, simultaneous and continuous quantitative measurement ofsolution pH and ammonia, and to novel methods and devices for measuringammonia in air or in solution.

BACKGROUND

Two forms of ammonia are present in any aqueous environment (e.g.,aquarium, pool, hot tub, lake, river, pond, manufacturing container,etc.). Ammonia (NH₃), sometimes referred to as ‘toxic ammonia,’ isnormally present in lower concentrations than ammonium ion (NH₄ ⁺),which is considered to be less toxic. ‘Total ammonia’ refers to the sumof ammonia plus ammonium ion levels in a solution.

It is important to know the ammonia concentration in a solution,particularly in an environment where organisms are present, due to itstoxicity. Most current visual tests, however, are only capable ofmeasuring ‘total ammonia’ (NH₃ plus NH₄ ⁺). These provide an indirectmeasure of the ammonia (NH₃) concentration, and are therefore at leastrelevant in estimating, for example, toxic ammonia (NH₃) levels in anaqueous system (e.g., aquarium, pool, hot tub, lake, river, pond,manufacturing container, etc.).

The relative levels of the two forms of ammonia (NH₃ and NH₄ ⁺) change,equilibrating between forms, with changes in pH and temperature. The pHeffect on the equilibrium between ammonia and ammonium concentration,described by a derivation of the Henderson-Hasselbach equation, is aexponential function:

$\lbrack {{NH}3} \rbrack = \frac{\lbrack {{NH}4} \rbrack}{10^{({{ph} - {pKa}})}}$Consequently, small changes in the pH result in large changes in theequilibrium balance of the two forms of ammonia. Similarly, temperatureeffects on the NH₃:NH4 equilibrium constant (pKa) which in turn affectsinterpretation of the Henderson-Hasselbach relationship and predictionof the solution concentration of NH₃ Ultimately, the amount of ammoniarises with increases in pH and solution temperature. Sampling variationarising as a result of variation in the temperature, time, and samplingposition/location within a given aqueous environment will therefore makeinterpretation of the Henderson-Hasselbach relationship incorrect.Therefore, in addition to knowing the ammonia content, it is importantto know the ammonium (NH₄ ⁺) and/or total ammonia (NH₃ plus NH₄ ⁺) levelto understand potential toxic risk in an aquatic system. In conditionsinvolving high ammonium content and low pH, a rise in pH would result ina subsequent large equilibration shift of NH₄ ⁺ into a high level oftoxic NH₃, quickly creating a hazardous situation.

In theory, if the concentration of either the ammonia, or the ammonium,or the total ammonia is determined through testing, in conjunction withthe pH of a solution, and the temperature is known, then based on theequilibrium relationship, the concentration of the other parameters canbe established. In practice, since both the nitrogenous products inwater (e.g., ammonia), temperature and pH levels can constantly vary,and in view of inherent limitations of existing test methods, themeasurement and tracking over time of these fluctuating parameters isproblematic, particularly with the simple procedures and kits typicallyused.

Current visual tests for ‘total ammonia’ and pH rely almost exclusivelyon single-point measurements, typically performed with an extricateddiscrete sample of the solution to be tested. Additionally, most requireaddition of reagents that engender non-reversible chemical reactions.Alternatively, there are single-use devices that can be immersed brieflyin a solution to be tested, without removing a test aliquot, but containreagents that are soluble, and that leach, bleed or diffuse from thesensing device. Such devices are only used for instantaneousmeasurements, at one time point, and are not designed for reversibilityor stability with prolonged immersion. Prior art examples of suchsingle-point pH test kits include: a freshwater only pH test kitrequiring a sample aliquot of freshwater and using a liquid reagent(Aquarium Pharmaceuticals, Inc.), where the product is only useful forfreshwater because its range is too narrow to be applicable tosaltwater, which typically has higher pH levels; and a pH dip test usinga test strip with an indicator reagent pad (Quick Dip™ pH test; JungleLaboratories Corporation); and a pH dip test using non-bleedingsingle-test indicator strips (e.g., COLORPHAST® pH 6.5-10.0; made by EMDChemicals, Inc. Gibbstown, N.J., USA). Additionally, there is one‘in-tank’ pH sensor that is a continuous in-tank freshwater only pHsensor (LivepH™ from LiveMeter™ Technologies, Inc.).

Prior art examples of such single point ammonia test kits include: atotal ammonia freshwater-only test kit requiring a sample aliquot offreshwater, and using a liquid reagent (Aquarium Pharmaceuticals, Inc.);and a total ammonia test using a test strip with an indicator reagentpad (Ammonia Test Strips, from Mardel). Additionally, one visual testfor directly measuring, at least qualitatively, only the toxic ammonia(NH₃) has also been developed, which is a continuous in-tank ammonia(NH₃) sensor (Ammonia Alert™, from Seachem).

Therefore, on the one hand, a total ammonia value obtained using a‘total ammonia’ single-point test kit, is somewhat useful in monitoringfor potentially toxic conditions. However, depending on parameters suchas pH, temperature and spatial positioning where the point measurementis made within an aqueous environment, such total ammonia measurementscan be indefinite and/or misleading, with respect to what the actualtoxic ammonia level is. On the other hand, prior art determinations oftotal ammonia, based on independent separate determinations of pH andammonia, are inherently inaccurate because of thermal, temporal andspatial inhomogeneity; for example, where multiple independent testsamples are withdrawn for either pH or ammonia (or for either pH andtotal ammonia) for testing at differing times from a larger aqueousenvironment. Additionally, the ‘read-out’ of prior art ammoniameasurement devices (the AMMONIA ALERT™ card of SEACHEM™) is qualitative(e.g., safe, dangerous, toxic) and not quantitative, precluding accuratedeterminations of ammonia (NH₃) concentration.

Therefore, prior art methods and devices for measuring ‘total ammonia’do not provide for accurate determination of ammonia, and independentprior art determinations of pH and ammonia have not afforded accuratequantitative determination of either ammonia or total ammonia (NH₃ plusNH₄).

Therefore, there is a pronounced need in the art for novel andcost-effective methods and devices for accurately determining pH,ammonia (NH₃) and total ammonia (NH₃ plus NH₄ ⁺) in an aqueousenvironment, and which overcome prior art inaccuracies relating tonon-homogeneous sampling, and to spatial, temporal and thermal samplingdiscontinuities. There is a pronounced need in the art for novel andcost-effective methods and devices for accurate quantitative andcontinuous determination of pH, ammonia (NH₃) and total ammonia (NH₃plus NH₄ ⁺) in an aqueous environment.

There is, in view of its potential toxicity, also a pronounced need inthe art for more sensitive devices and methods to quantitatively measureammonia to provide for earlier detection of potential problems in bothsolution (e.g., aqueous) and air environments.

SUMMARY OF THE INVENTION

Particular aspects provide novel methods and devices for accuratelymeasuring total ammonia (NH₃ plus NH₄ ⁺) in a solution by proximate,simultaneous and continuous quantitative measurement of solution pH andammonia. The inventive proximate, simultaneous and continuous solutionmeasurement devices are unique, and overcome inaccuracies of the priorart relating to non-homogeneous sampling, and to spatial, temporal andthermal sampling discontinuities that give rise to inaccurate ammonia,and total ammonia determinations.

Additional aspects provide novel ultra-sensitive ammonia detectiondevices and methods for using same.

Particular embodiments provide a combination pH and ammonia measuringdevice for simultaneous, continuous measurement of solution pH andammonia, comprising: a submersible member, suitable to be at leastpartially submersible in a solution; a submersible ammonia-sensingportion attached to the submersible member, the ammonia-sensing portionhaving non-dissociating detection means suitable to provide for acontinuous visual indicator of solution ammonia concentration; asubmersible pH-sensing portion attached to the submersible member, thepH-sensing portion having non-dissociating detection means suitable toprovide for a continuous visual indicator of solution pH; a visualammonia indicator comparison means, comparable with the continuousvisual indicator of the ammonia-sensing portion for standardizedquantitative determination of solution ammonia concentration; and avisual pH indicator comparison means, comparable with the continuousvisual indicator of the pH-sensing portion for standardized quantitativedetermination of solution pH.

Additional embodiments provide a combination pH and ammonia measuringdevice for simultaneous, continuous measurement of solution pH andammonia, comprising: an attachment base member; a submersible member,reversibly attachable to the attachment base member, and suitable to beat least partially submersible in a solution; a submersibleammonia-sensing portion attached to the submersible member, theammonia-sensing portion having non-dissociating detection means suitableto provide for a continuous visual indicator of solution ammoniaconcentration; a submersible pH-sensing portion attached to thesubmersible member, the pH-sensing portion having non-dissociatingdetection means suitable to provide for a continuous visual indicator ofsolution pH; a visual ammonia indicator comparison means, comparablewith the continuous visual indicator of the ammonia-sensing portion forstandardized quantitative determination of solution ammoniaconcentration; and a visual pH indicator comparison means, comparablewith the continuous visual indicator of the pH-sensing portion forstandardized quantitative determination of solution pH.

Yet further embodiments provide a method determining the total ammoniaconcentration in a solution, comprising: submersing, in a solution, acombination pH and ammonia measuring device for simultaneous, continuousmeasurement of solution pH and ammonia; and determining the totalammonia (NH₃ plus NH₄ ⁺), based on a visual indicator of solutionammonia concentration and a visual indicator of solution pH. Preferably,the combination pH and ammonia measuring device for simultaneous,continuous measurement of solution pH and ammonia are as disclosedherein.

Yet further embodiments provide an ammonia detection device, comprisingporous matrix polytetrafluoroethylene (PTFE) having an ammonia-sensitiveimmobilized dye, the immobilized dye suitable to provide for acolorimetric determination of ammonia level, and wherein the detectiblerange of ammonia comprises a range of about 0.005 to about 0.1 ppm.Preferably, the ammonia-sensitive immobilized dye is BPB dye.Preferably, the porous matrix polytetrafluoroethylene (PTFE) comprises acomposite supported microporous PTFE medium, comprising a PTFEmicroporous membrane having secured directly to at least one facethereof a PTFE web of microfibres.

Additional embodiments provide a method for detecting ammonia in air,comprising exposing the above-described ammonia detection device to air,wherein a colorimetric determination of air ammonia level is, at leastin part, afforded. Particular aspects of this method comprise opticalsensing to interrogate the color of the ammonia-sensitive immobilizeddye.

Further embodiments provide a method for detecting ammonia in solution,comprising exposing the above-described ammonia detection device to atest solution, wherein a colorimetric determination of solution ammonialevel is, at least in part, afforded. Particular aspects of this methodcomprise optical sensing to interrogate the color of theammonia-sensitive immobilized dye.

Yet further methods comprise enhanced sensitivity sensors, comprisingporous matrix polytetrafluoroethylene (PTFE) having one or moreimmobilized indicator dyes to provide for an enhanced colorimetricdetermination of detected substance. In particular aspects, the porousmatrix polytetrafluoroethylene (PTFE) comprises a composite supportedmicroporous PTFE medium, comprising a PTFE microporous membrane havingsecured directly to at least one face thereof a PTFE web of microfibres.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-D show exemplary embodiments of a combination pH and ammoniameasuring device according to particular aspects of the presentinvention. FIGS. 1A-1D show a combination sensor strip as a standalonesensor strip (FIGS. 1A and 1D, in gray-scale and color, respectively),and as reversibly attached to a sensor card having integral color charts(FIGS. 1B and 1C, in gray-scale and color, respectively).

FIG. 2 shows, according to particular aspects of the present invention,the exemplary combination pH and ammonia measuring device embodiment ofFIG. 1D (standalone sensor strip, the being used to continuously measurepH and ammonia in an aqueous environment (e.g., aquarium, pool, hot tub,lake, river, pond, manufacturing container, etc.).

FIG. 3 shows, according to further aspects of the present invention,another exemplary combination pH and ammonia measuring deviceembodiment.

FIG. 4 shows, according to yet further aspects of the present invention,another exemplary combination pH and ammonia measuring deviceembodiment.

DETAILED DESCRIPTION OF THE INVENTION Definitions

With respect to proximate, simultaneous, continuous measurement ofsolution pH and ammonia using the at least one pH-sensing and the atleast one ammonia-sensing portions of the present inventive devices, theterm “proximate” refers to the fact that the at least oneammonia-sensing portion, and the at least one pH-sensing portion are:(i) relatively disposed in a close, near, adjacent or adjoining spatialrelationship to one another, but not necessarily contiguous; and (ii)are integral with or attached to a submersible member, or a plurality ofproximately connected, coordinately-submersible members, such thatsensors are coordinately and proximately submersible in the solution tobe tested. Accordingly, with respect to the submersible member, or theplurality of proximately connected, coordinately-submersible members,the term “submersible” refers to the fact the member or proximatemembers must be at least partially submersible in a solution; that is,must be sufficiently submersible to enable coordinate, proximatesubmersion of the integral or attached sensing portions.

With respect to proximate, simultaneous, continuous measurement ofsolution pH and ammonia using the at least one pH-sensing and the atleast one ammonia-sensing portions of the present inventive devices, theterm “simultaneous,” as used herein refers to concurrent or coincidentin real-time measurement of pH and ammonia by the proximate,coordinately submersed pH-sensing and ammonia-sensing portions.Therefore, while pH and ammonia are measured using separate butproximate sensing portions, the sensing of pH and ammonia is concurrentor coincident in real-time as enabled by the instant inventive devices.Significantly, the instant proximate, simultaneous and continuoussolution measurement devices are unique, and overcome inaccuracies ofthe prior art relating to non-homogeneous sequential sampling, and tospatial, temporal and thermal sampling discontinuities that give rise toinaccurate total ammonia determinations.

With respect to proximate, simultaneous, continuous measurement ofsolution pH and ammonia using the at least one pH-sensing and the atleast one ammonia-sensing portions of the present inventive devices, theterm “continuous” refers to the fact that, in each case, the at leastone ammonia-sensing portion, and the at least one pH-sensing portionare: (i) sufficiently stable to be submersed within the solution beingtested over an extended time (e.g., minutes, hours, days, weeks, months,years; preferably, weeks, months or years; most preferably months oryears) without substantial deterioration (e.g., bleeding, break-down,etc.) of the indicator means (e.g., visual indicator means); and (ii)the detection means is ‘reversible’ in the sense that the pH and ammoniadetection means is in sufficient equilibrium with the test solution soas to continuously track or reflect changes (e.g., real-time changes) inpH and ammonia, respectively, as the pH and ammonia values vary (e.g.,reversibly increasing or decreasing) within the detectable range of therespective sensors.

As described in relation to continuous measurement, “stable detectionmeans,” as used herein refers to the fact that, in each case, the pH andammonia-sensing portions are sufficiently stable so as to be submersiblewithin the solution being tested over an extended time withoutdeterioration (e.g., bleeding, break-down, etc.) of the indicator means(e.g., visual indicator means) to an extent that would render the devicedysfunctional for providing accurate pH and ammonia determinations.Preferably, an extended time refers to minutes, hours, days, weeks,months, or years. Preferably, an extended time refers to days, weeks,months, or years. More preferably, an extended time refers to days,weeks, months, or years. Most preferably, an extended time refers toweeks, months, or years, without deterioration of the indicator means toan extent that would render the device dysfunctional for providingaccurate pH and ammonia determinations. Preferably, the stable pH andammonia indicator means are stable visual indictor means. In particularaspects, the stable visual indicator means comprise pH-sensitive, orammonia-sensitive dyes (e.g., colorimetric dye indicators) that providefor visual colorimetric determinations of pH and ammonia, respectively.

“Comparison means,” as used herein refers to at least one comparisonmeans to be used in combination with the respective indicator means(e.g., visual, colorimetric dyes, etc.) to provide for standardizedquantitative determination of solution concentration, in contrast to thelimited qualitative information of prior art devices (e.g., such as theAMMONIA ALERT™ card of SEACHEM™, that has, for example, color blockscorresponding to ‘presumptive safe,’ ‘dangerous’ or ‘toxic’ levels).Suitable comparison means may take a variety of forms, including but notlimited to charts, curves, tables, graphs, etc. Preferably, the at leastone comparison means comprise a linear color-gradient chart, and/orcomprise a circular color-gradient or wheel color-gradient chart. Inparticular embodiments, more than one comparison means is provided foreach respective indicator means (e.g., for each respective sensingportion). The comparison means can be integral with or attached (e.g.,reversibly attached) to the submersible member, the proximatesubmersible members, or the attachment base member.

“Movably comparable” as used herein refers to comparison meanscomprising a comparison chart (e.g., ammonia or pH reference colorindicator comparison charts) that is separate or separable from therespective sensing portion, but can be positioned near the respectivesensing portion and optionally moved in relation thereto to facilitatevisual comparison (e.g., comparative matching of a color bar orcolor-gradient chart with the indicator color of the respective sensingportion.

“Relational means,” as used herein in the context of quantitativelydetermining total ammonia (NH₃ plus NH₄ ⁺), refers to relational means(e.g., charts, graphs, tables, formulas, algorithms, etc.) to facilitatequantitative determination of total ammonia (NH₃ plus NH₄ ⁺), based onthe visual indicators of solution ammonia and pH, in combination withthe respective quantitative ammonia and pH comparison means.

Aspects of the present invention relate generally to methods and devicesfor measuring the status of an aqueous environment (e.g., freshwater andsaltwater). Particular aspects provide novel methods and devices forproximate quantitative measurement of pH, and ammonia, enabling accuratequantitative determination of ‘total ammonia’ (NH₃ plus NH₄ ⁺) in asolution; specifically, by proximate, simultaneous and continuousquantitative measurement of solution pH and ammonia (NH₃). The methodsprovide a substantial advantage over relatively inaccurate, qualitativeprior art devices, and can be used in freshwater and saltwater.

Preferred aspects comprise detection means having visual indicator means(e.g., colorimetric dyes, etc.) in combination with comparison means toprovide for standardized quantitative determination of solutionconcentration, in contrast to the limited qualitative information (e.g.,presumptive safe, dangerous or toxic levels) of prior art devices (e.g.,such as the AMMONIA ALERT™ card of SEACHEM™). Quantification of ammoniais important, because it enables users to accurately know the toxicammonia concentration and reach conclusions about the risk level,potential problems and toxicity, and with respect to nitrate/nitriteissues of the tested aqueous solution (e.g., in the context of organisms(e.g., fish, plant life, etc.) being held or reared in an aquarium,pond, container, etc.). Additionally, quantification of ammonia enablesthe determination of solution ‘total ammonia’ (NH₃ plus NH₄ ⁺).Significantly, by proximate, combined ammonia and pH measurements,quantitative determinations of both parameters are made simultaneously,in the same or proximate solution place, and with exposure to the sameaqueous environment (e.g., temperature, interfaces, surfaces,vegetation, sources of air or other gases, etc), thereby providing amore accurate determination of the solution status, which isparticularly important for accurate, reliable determination of ‘totalammonia.’

In preferred embodiments, ammonia and pH sensor portions are proximatelycombined on a single submersible member, or combined on a plurality ofproximate, coordinately-submersible members, to enable measurement andquantitative determination of both pH and ammonia concentration at thesame time, temperature and position of an aqueous environment),providing a more accurate quantitative determination of the solutionstatus, particularly that of ‘total ammonia’ (NH₃ plus NH₄ ⁺), than hasheretofore been possible. The sensor portions can, in each case, beintegral with the submersible member or proximate submersible members,attached to the submersible member or proximate submersible members, orreversible attached to the submersible member or proximate submersiblemembers to facilitate replacement or attachment of additional sensors(e.g., to replace a sensor, and/or to add an additional ammonia and/orpH sensor covering a different or overlapping range of solution ammoniaconcentrations and/or pH ranges, respectively). In particular aspects, avisual ammonia indicator comparison means is attached (e.g., reversibly)to or integral with the submersible member or proximate submersiblemembers. The ammonia indicator means is comparable with the continuousvisual indicator of the ammonia-sensing portion for standardizedquantitative determination of solution ammonia concentration. Inparticular embodiments, a visual pH indicator comparison means isattached (e.g., reversibly) to or integral with the submersible memberor proximate submersible members. The pH indicator means is comparablewith the continuous visual indicator of the pH-sensing portion forstandardized quantitative determination of solution pH.

In preferred embodiments, the continuous visual indicator of theammonia-sensing portion, and/or the continuous visual indicator of thepH-sensing portion, comprises a colorimetric dye indicator. Inparticular aspects, the visual ammonia indicator comparison meanscomprises an ammonia reference color indicator comparison chart integralwith or attached (e.g., reversibly) to the submersible member orproximate submersible members. Alternatively, the visual ammoniaindicator comparison means may comprise an ammonia reference colorindicator comparison chart that is separate from, but movably comparableto the ammonia-sensing portion of the submersible member or proximatesubmersible members. Preferably, the ammonia reference color indicatorcomparison chart comprises a color-gradient indicator comparison chart(e.g., linear color-gradient chart, or a circular or wheelcolor-gradient chart).

In preferred embodiments, the visual pH indicator comparison meanscomprises a pH reference color indicator comparison chart integral withor attached (e.g., reversibly) to the submersible member or proximatesubmersible members. Alternatively, the visual pH indicator comparisonmeans comprises a pH reference color indicator comparison chart that isseparate from, but movably comparable to the pH-sensing portion of thesubmersible member or proximate submersible members. Preferably, the pHreference color indicator comparison chart comprises a color-gradientindicator comparison chart (e.g., a linear color-gradient chart, or acircular or wheel color-gradient chart).

In particularly preferred embodiments, the combination pH and ammoniameasuring devices for simultaneous, continuous measurement of solutionpH and ammonia further comprise relational means (e.g., charts, curves,tables, graphs, etc) for quantitatively determining total ammonia (NH₃plus NH₄ ⁺), based on relating the visual indicator of solution ammoniaconcentration and the visual indicator of solution pH, in combinationwith the respective quantitative ammonia and pH comparison means. Suchindirect, relational embodiments provide for accurate determination ofpH, ammonia, and ‘total ammonia.’ Alternatively, the inventivecombination devices can be used for directly determining total ammoniaconcentration. For such direct applications the submersible member orproximate submersible members (e.g., strip sensors) are put into a testsample aliquot, along with an added agent to increase the pH, and theinventive sensors then provide a measure of total ammonia; because theammonium ion (NH₄ ⁺) is converted to ammonia (NH₃). The use of aplurality of ammonia sensors of different or overlapping range isparticularly preferred in such direct embodiments, because inconjunction with the higher pH, the ammonia levels measured will betotal ammonia levels that are much higher than the ammonia present inmost typical aqueous environment. For example, a bromocresol green (BCG)sensor, or chlorophenol red CPR) type sensor is employed. Additionally,even for such direct measurement of total ammonia, the presence of aproximate pH sensor in the same sample as is being tested for totalammonia has considerable value for confirming that the pH issufficiently high to adequately perform the reliable total ammonia test.Without the proximate pH sensor, the user would not otherwise know thatthe pH is sufficiently high without the additional need for independentmeasuring the adjusted solution with a separate non-proximate pH sensingmeans and the attendant uncertainties.

Significantly, the inventive methods and devices do not require removalof a test sample, or a plurality thereof to conduct analyses, thuseliminating inhomogeneous sampling and testing errors and discrepanciesthat occur where one or more smaller solution test samples are taken,serially in time, from different special positions within a largeraqueous environment to be tested at different times, temperatures, pH,and/or proximity to other sources of inhomogeneity (e.g., interfaces,surfaces, vegetation, sources of air or other gases, etc) in the aqueousenvironment. Accurate status determinations are particularly importantin making reliable total ammonia measurements and determinations basedon the pH and NH₃ levels.

Preferred embodiments provide combination pH and ammonia measuringdevices for simultaneous, continuous measurement of solution pH andammonia, comprising a unique ultra-high sensitivity visual ammoniasensor, heretofore not described, capable of providing accurate measuresof ammonia in a lower ppm range that could be previously detected, suchthat the measurements can be indicative of a developing problem and/orpotential toxic condition that was heretofore not predictable. Inpreferred embodiments of the invention, the enhanced sensitivity toammonia detection is provided by immobilizing one or more indicator dyesin porous matrix polytetraflouroethylene (PTFE). For example, anindicator dye is immobilized in a composite supported microporous PTFEmedium, comprising a PTFE microporous membrane having secured directlyto at least one face thereof a PTFE web of microfibres. In preferredaspects, bromophenol blue (BPB) dye is immobilized in a special porousmatrix polytetrafluoroethylene (PTFE) material (ZEFLUOR™, Pall Gelman,Ann Arbor, Mich.; see U.S. Pat. No. 5,366,631 entitled “Composite,Supported Fluorocarbon Media,” and incorporated herein by reference inits entirety; see also U.S. Pat. Nos. 3,953,566 and 4,187,390(describing PTFE membranes) and U.S. Pat. No. 4,716,074 (describing PTFEweb), all of which are incorporated herein by reference in theirentirety), or the functional equivalent thereof, to form an ammoniasensor, which yields a higher ammonia sensitivity (e.g., in the range ofabout 0.005 to about 0.1 ppm) than previously reported (e.g., having asignificantly higher sensitivity than BPB in another PTFE substrates,such as TEFLON™ tape produced by St. Gobain).

ZEFLUOR™ (PTFE with a PTFE support) comprises a web of fluoropolymericmicrofibers secured to a fluoropolymeric microporous membrane. Thecomposite, supported microporous membrane is free of any adhesivecomponents, the membrane being secured (by bringing the material to“fusion temperature” and application of sufficient pressure to achievebinding of the membrane to the microfiber material) to the web solely atthe interfaces of the membrane and the web (see U.S. Pat. No.5,366,631). ZEFLUOR™ is available in a variety of pore sizes andthicknesses: for example, 0.5, 1, 2, 3 μm pores, with the followingrespective thickness 0.5 μm (178 μm; 7 mils thick); 1 μm (165 μm; 6.5mils thick); 2 and 3 μm (152 μm; 6 mils thick) and 5 μm (127 μm; 5 milsthick). ZEFLUOR™ and ZYLON™ (unsupported PTFE) offer low chemicalbackground for highly sensitive determinations. In particular aspects, 3μm Zefluor PTFE (Teflon) microporous membranes are used, having amicroporous Teflon layer approximately 15 μm thick mounted onto a 165 μmthick Teflon macroporous substrate, for a total thickness of 180 p.m.The porosity of the 15 μm microporous layer is calculated to be 44%,based on void volume information obtained from Gelman.

Therefore, while in particular aspects, the ammonia-sensing portion ofthe inventive devices is suitable to detect ammonia in the range ofabout 0.05 to about 0.5 ppm, or about 0.05 to about 1.0 ppm, preferably,the ammonia-sensing portion of the inventive devices is suitable todetect ammonia in the range of about 0.005 to about 0.1 ppm, or about0.005 to about 0.05 ppm, or from about 0.005 to 0.05 ppm. Significantly,provision of such ultra-high sensitivity ammonia sensors (e.g., in therange of about 0.005 to about 0.1 ppm, or about 0.005 to about 0.05 ppm,or from about 0.005 to 0.05 ppm, or about 0.005 ppm to about 0.01 ppm,or from 0.005 ppm to 0.01) in combination, or proximate combination,with a pH sensor has not previously been described. Therefore, inparticular embodiments, the device is capable of detecting ammonialevels as low as about 0.005 ppm.

In particular aspects, the inventive devices may comprise a plurality ofpH or ammonia sensors representing different detection ranges (e.g., aplurality of ammonia sensors, representing different ammonia detectionranges). For example, in particular aspects the device comprises a pHsensor portion, in combination with two ammonia sensing portions, wherethe ammonia sensing portions are sensitive to different or overlappingconcentration ranges of ammonia. As stated above, the sensor portionscan, in each case, be integral with the submersible member or proximatesubmersible members, can be attached to the submersible member orproximate submersible members, or can be reversible attached to thesubmersible member or proximate submersible members to facilitatereplacement or attachment of additional sensors (e.g., an additionalammonia sensor covering a different or overlapping range of solutionammonia concentrations). Use of two or more visual sensors (e.g.,ammonia sensors) of different but overlapping ranges of ammoniasensitivity not only provides a wider range of measurable solutionammonia concentration, but also affords increased accuracy andreliability of measures by having two color-matches to pinpoint anddetermine the ammonia concentration.

Particular aspects provide a combination pH and ammonia measuring deviceas described and disclosed herein, comprising a plurality of submersibleammonia-sensing portions, wherein at least two of the ammonia sensingportions have different ammonia sensitivities. In particularembodiments, the at least two ammonia sensing portions having differentammonia sensitivities each have a different sensitivity range selectedfrom the ammonia sensitivity range group consisting of about 0.05 toabout 0.5 ppm, about 0.05 to about 1.0 ppm, about 0.005 to about 0.1ppm, about 0.005 ppm to about 0.05 ppm, about 0.005 ppm to 0.05 ppm,about 0.005 to about 0.01, or from about 0.005 to 0.01. Certainembodiments comprise at least three submersible ammonia-sensing portionseach having a different ammonia sensitivity or sensitivity range. Inparticular implementations, the at least three ammonia sensing portionshaving different ammonia sensitivities each have a different sensitivityrange selected from the ammonia sensitivity range group consisting ofabout 0.05 to about 0.5 ppm, about 0.05 to about 1.0 ppm, about 0.005 toabout 0.1 ppm, about 0.005 ppm to about 0.05 ppm, and about 0.005 ppm to0.05 ppm.

Therefore, certain embodiments comprise two or three ammonia sensor,and/or pH sensor elements into a signal device with each sensor of agiven sensor type (e.g., pH or ammonia) having a different sensitivity,and further showing a different color in response to a given level ofNH3 (or to a given pH value in the case of multiple pH sensors havingdifferent sensitivities or different ranges thereof).

According to particular aspects, such ‘compound range’ embodimentsprovide at least two primary advantages. First, the useful sensing rangeof the devices is increased, enabling readout over a wider scale.Second, the interpretive ease and accuracy of the readout issubstantially enhanced, because it is easier and more accurate to matcha pair, for example, of different colors of two sensors against areference color-chart with respective paired colors, than it is todiscriminate a single sensor's color against a chart with subtle huedifferences between close ammonia concentrations, or close pH values.These aspects provide a solution to a rather common problem with singlesensors. For example, prior art pH and NH₃ sensors don't exhibit markedchanges through different colors (e.g. from yellow to green to blue).They only shift from a baseline yellow to very little green and thendarker shades of green with increasing ammonia.

In particular aspects, the inventive combination pH and ammoniameasuring devices for simultaneous, continuous measurement of solutionpH and ammonia comprise a submersible member, or a plurality ofproximately connected, coordinately-submersible members, suitable to beat least partially submersible in a solution. Solution status sensors(e.g., pH and/or NH₃) are integral with, attached to, or reversiblyattached to the submersible member or to the plurality of proximatesubmersible members, such that submersion of the submersible member orthe plurality of proximate submersible members enables continuouscoordinate proximate submersion of the integral and/or attached sensorsinto the solution environment to be tested. In particular aspects, thesubmersible member or the plurality of proximate submersible memberscomprise one or more submersible strips, with the sensor componentsintegral with, and/or attached to (e.g., reversibly attached to) thesubmersible strip or proximate submersible strips. In particularaspects, sensors can be replaced on a submersible strip, or additionalsensors can be added to a strip.

In particular preferred aspects, the combination pH and ammoniameasuring devices for simultaneous, continuous measurement of solutionpH and ammonia comprise an optionally attachable attachment base member(e.g., immersible indicator card) that may be nonsubmersible, oroptionally submersible or partially submersible. In certain of suchembodiments, the above-described submersible member or proximatesubmersible members having the sensor means, are reversibly attachableto the attachment base member, so that the submersible member orproximate submersible members can be detached (e.g., for aesthetic, orspatial reasons) from the attachment base member for coordinatesubmersion of the sensors in the solution, without the presence of thelarger attachment base member. Therefore, in particular embodiments, thesubmersible member or proximate submersible members (e.g., strips havingpH and ammonia sensor portions) can be attached to a companionattachment base member (e.g., immersible-indicator card) for convenientreading by color-matching with a comparative standard indicator guide(e.g., color chart) located on the attachment base. Alternatively, anduniquely, the submersible member or proximate submersible members (e.g.,strips having pH and ammonia sensor portions) can be detached from theattachment base member (e.g., from the immersible-indicator card) forindependent use, providing for a smaller and less obtrusive combinationsensing device. In such alternative embodiments, the comparativestandard indicator chart, or charts, can be held and/or moved in theproximity of the respective sensors for color-matching for making aquantitative determination of the ammonia and pH values. Additionally,the removable/detachable, submersible member or proximate submersiblemembers (e.g., strip-sensor component) enables the sensors to be placed,if desired, in a small volume test sample for discrete sample testing,for instance, of an aliquot put in a small volume test tube.Alternatively, the submersible member or proximate submersible memberscan be detached from the attachment base member and used in the primarysolution, where a user desires less obtrusive measuring means (e.g., ina aquarium, landscaping ponds, etc.).

For purposes of the present invention, the submersible member, theproximate coordinately-submersible members, or the attachment basemember can be totally or partial submersed, the only requirement beingthat they are submersible to an extent sufficient to allow forcoordinate submersion of the integral or attached sensors. In particularembodiments, the measuring devices further comprise at least onepositioning element for positioning the device within the test solution.In certain embodiments, the at least one positioning element articulateswith the submersible member or proximate coordinately submersiblemembers to position the member or members so that they can be viewed bya user. Alternatively, the positioning element articulates with theattachment base member. In certain embodiments, the position elementarticulates with an orifice in the submersible member and/or theattachment base member. A variety of different positioning elements aresuitable for use in positioning the submersible member or attachmentbase member for viewing by a user, including buoyancy elements (e.g.,floats), suction cups, adhesives, hooks, clips, snaps, tethers, magnets,etc. For example, a float or suction cup may be articulated with anorifice in the top of a submersible member, or attachment base member toposition the device at a convenient viewer-friendly position within thesolution being tested.

In particular aspects, as discussed briefly above, more accurate andreliable visual determinations are enabled by providing a color-gradientindicator approach, rather than merely color-block matching.Color-gradient indicator comparison charts enable the eye to make moreprecise color matching, whereas block color matches are difficult toperform when the color of the sensor does not exactly match a providedindicator color-block color. In particular aspects, even more accurateand precise color matching is afforded by providing a large colorgradient that can be moved or changed in presentation with respect tothe respective sensor. Preferably, the color-gradient chart is orcomprises at least one of a linear color gradient, or a circular or‘wheel’-gradient.

As will be appreciated in the relevant art, bright light, in particularsunlight, as might be encountered when using sensors in outdoor pondsand pools, may pose a problem in that direct exposure to sunlight maycause a significant degradation of sensors over time. Therefore,according to particular aspects of the present invention, protectionfrom sunlight or otherwise even bright aquarium lighting is ofconsiderable significance in providing a viable product for outdoorapplications.

Particular embodiments, therefore, associate or incorporate at least onelight blocking aspect or member to reduce the effect of light (e.g.,aquarium lights) that might cause bleaching of the sensor dyes, or theinks used to create the comparative standard indicator guide (e.g.,color chart located on the attachment base). In particular aspects, thelight blocking aspect encompasses a light-absorbing or reflective shieldor shroud around the device (e.g., prior art devices or those disclosedherein) with an unobscured region for viewing the device sensors.Alternatively, light absorbing or reflective paints or coatings areapplied to the backside, or a non-viewing side of the submersibleelements. In yet further aspects, therefore, UV absorbing agents (e.g.,art-recognized UV blocking films) of such types commonly used inpolymers and coatings in the printing industry to reduce bleaching orfading of inks and dyes exposed to light, are associated with, orincorporated into the submersible elements or specifically the ammoniasensing or pH sensing portions (e.g., placed over or around the sensorsin a manner that yet allows circulation of the solution or test water,etc., around the sensor) to provide shielding benefit. Additionalaspects provide for association and/or incorporation of visible lightblocking agents.

In additionally aspects, reflective films, such as metalized polymers(e.g., Mylar) are used for light shielding and have been shown byapplicants to be significantly beneficial in practicing aspects of thepresent invention. For such reflective films, the effectiveness wasdetermined to be proportional to the density of the light absorbing orreflective aspects thereof.

In preferred aspects, a cover over and/or around the sensors usingtotally light-blocking material is used. In particular aspects, thecover comprises a black plastic hood or shroud placed over the top ofthe sensor device. In additional aspects, a black plastic cylinderencompassing the sensor device is used (e.g., that the sensor deviceslides down inside). Although, such ‘light protected’ sensors precludecasual viewing because they at least partially obscure the sensor, theyare nonetheless useful, particularly where they can be easily lifted toallow for casual viewing of the sensor, and particularly where suchsensors are significantly longer lasting that non-protectedcounterparts. Additionally, such sensors are particular valuable whereinfrequent viewing of the sensor is sufficient, such as in more stableaqueous environments.

Therefore, according to additional aspects, there are many shapes,forms, and configurations for light shielding means that can be designedwhich meet the two constraints of UV and/or visible light-blocking andyet allowing water to reach and circulate around the sensor (e.g., ofboth art-recognized and presently disclosed sensor devices).

Suitable pH indicator dyes are known in the relevant art, and preferredexemplary pH indicator dyes (along with respective effective pH ranges)include, but are not limited to: Bromocresol Purple pH 5.2-6.8);Bromothymol Blue (pH 6.0-7.6); Phenol Red (pH 6.8-8.4); Thymol Blue (pH8.0-9.6). Various pH-sensing materials of suitable stability (e.g.,non-bleeding, or substantially so) for use in the present inventivecontinuous measurement embodiments are known in the art. In particularaspects the submersible pH-sensing portions comprise non-bleeding pHindicator strips (e.g., COLORPHAST® pH 6.5-10.0; made by EMD Chemicals,Inc. Gibbstown, N.J., USA; or other polymer-based pH sensors such asthose made by “ph-ion”, and “Livemeter”). Various measurable pH ranges(and respective sensor portions and indicator means) are encompassedwithin the scope of the present invention, including but not limited to:about pH 5 to about pH 9.5; about pH 5.5 to about pH 9; about pH 6 toabout pH 9; about pH 6.5 to about pH 8.7. Preferably, the pH range isabout pH 6 to about pH 9; or about pH 6.5 to about pH 8.7. Preferably,the pH range is about pH 6 to about pH 9. Preferably the range is onesuitable to span freshwater and saltwater conditions.

With respect to visual ammonia sensing, regarding the ranges of use withdifferent dyes, pieces of sensor material large enough for viewing areexposed in an environment to be monitored for ammonia. In addition tobromophenol blue (BPB), stable sensor compositions comprisingbromocresol green (BCG) as the ammonia-sensitive indicator dye exhibit,in solution, a reversible color change from yellow towards blue-green tofinally a blue hue when exposed to ammonia of respectively increasingconcentration (e.g., in the range of 0 to about 5 ppm or greater).Likewise, chlorophenol red (CPR) has utility as an ammonia sensitiveindicator dye, and exhibits a reversible color change in solution fromorange towards magenta and eventually a purple hue when exposed toammonia of increasing concentration (e.g., in the range of 0 to about 10ppm or greater). Sensor material can be immersed directly into aqueoussamples for monitoring ammonia. In particular aspects the sensors areused for sensing ammonia in air. Preferably, the sensor material (dyesubstrate) is PTFE (e.g., TEFLON®).

In particular embodiments, the ammonia sensors are made as described inU.S. patent application Ser. No. 09/157,209 (pub. no. 20030003589),which in incorporated by reference herein in its entirety. Briefly, thesensor composition is made from an ammonia sensitive indicator dye and asolid phase, preferably a PTFE solid phase (e.g., film form). The sensorcompositions are constructed by administering ammonia-sensitiveindicator dye(s) in a non-aqueous solvent to a solid-phase PTFEsubstrate such that the dye is deposited on the solid phase in a forminsoluble to aqueous-based solvents (Id).

For example, ammonia-sensitive indicator dyes are dissolved in anappropriate (non-aqueous) solvent that will wet, penetrate, or dissolvethe PTFE substrate. Preferred solvents include, but are not limited totetrahydrofuran, ethanol, and methanol. The solvent serves as a“carrier” of the ammonia-sensitive indicator dye (or combinationsthereof) for application to PTFE solid phase substrates. Exemplarypreparations of dye solutions for preparing indicator films forapplications involving visual detection are: (a) bromocresol green(Aldrich #11,435-9), 100 mg dissolved in 20 ml methanol; (b)chlorophenol red (Aldrich #19,952-4), 100 mg dissolved in 20 mlmethanol; and (c) phenol red (Aldrich #11,452-9), 100 mg dissolved in 20ml methanol. Generally, solutions for preparing an ammonia-sensitiveindicator dye for application to a PTFE film that will be used foroptical measurements are made, for example, by dissolving 20 mg of thecorresponding dye in 20 ml methanol. Other exemplary suitable solutionpreparations that have been made include chlorophenol red (Aldrich#19,952-4), 22 mg dissolved in 10 ml tetrahydrofuran, bromophenol blue(Aldrich #11,439-1), 10 mg dissolved in 10 ml Ethanol, and bromocresolgreen (Aldrich #11,435-9), 20 mg dissolved in 10 ml tetrahydrofuran.

PTFE (Teflon®) is the preferred solid phase substrate. Thehydrophobicity of the PTFE provides a strong non-covalent bond to bondthe dyes. Ammonia diffuses through PTFE easily, and PTFE material can beeasily fabricated and cut into appropriate shapes or configurations forparticular sensing applications. PTFE tapes and film materials fromseveral different manufacturing sources have been used to fabricateinventive ammonia sensor compositions. Use of preformed solid-phasefilms, membranes, or tapes affords simple and economical manners offabricating of ammonia sensor compositions. A porous PTFE form ispreferred, to promote the faster penetration of the gaseous compoundinto the polymer and reaction with the ammonia sensitive indicator dyeimmobilized therein. Exemplary PTFE material manufactures whose productshave been used as PTFE substrates for sensor compositions in the form ofa film include, for example, PTFE thread seal tapes from PlastomerProducts Division (Newtown, Pa.), or Furon (Hoosick Falls, N.Y.), andporous PTFE films from Gore-Tex (Elkton, Md.). More preferably, asdescribed for the first time herein, the sensor material is comprisesporous matrix polytetrafluoroethylene (PTFE) having an ammonia-sensitiveimmobilized dye, the immobilized dye suitable to provide for acolorimetric determination of ammonia level. Preferably, theammonia-sensitive immobilized dye is BPB dye. Most preferably, theporous matrix polytetrafluoroethylene (PTFE) comprises a compositesupported microporous PTFE medium, comprising a PTFE microporousmembrane having secured directly to at least one face thereof a PTFE webof microfibres (e.g., ZEFLUOR™, Pall Gelman, Ann Arbor, Mich.; see U.S.Pat. No. 5,366,631 entitled “Composite, Supported Fluorocarbon Media,”and incorporated herein by reference in its entirety; see also U.S. Pat.Nos. 3,953,566 and 4,187,390 (describing PTFE membranes) and U.S. Pat.No. 4,716,074 (describing PTFE web), all of which are incorporatedherein by reference in their entirety), or the functional equivalentthereof). Preferably, the detectible range of ammonia using such porousmatrix polytetrafluoroethylene (PTFE) comprises a range of about 0.005to about 0.1 ppm, providing an ultra-sensitive ammonia detection devicethat is suitable to detect low amounts of ammonia in either solution, orin air.

A preferred method of fabrication is to dip the PTFE material (e.g., 2cm to 5 cm wide PTFE strips) into a bath of an indicator dye stocksolution. An “indicator stock solution” comprises an ammonia sensitiveindicator dye (or combinations thereof) dissolved in a non-aqueoussolvent. This allows ammonia sensitive indicator dye to adhere to thesolid phase PTFE to form a “wet” sensor composition. The wet sensorcomposition is dried at room temperature, or aided with forced air or adrier to facilitate solvent evaporation. The sensor composition (nowdried) is then immersed in a fuming 1N-hydrochloric acid solution for 10minutes. This is followed by a final rinse by immersion in water for 2minutes. The sensor composition is then left to dry.

Therefore, aspects of the present invention also provide anultra-sensitive ammonia detection device for detecting ammonium and/orvolatile amines in a gas or liquid state, comprising anammonia-sensitive indicator dye (e.g., BPB) having measurable spectralcharacteristics immobilized in or on a solid substrate, whereby exposureto a compound causes a change in spectral characteristics of the dye.Preferably, the solid substrate is porous matrix polytetrafluoroethylene(PTFE) (e.g., comprising a composite supported microporous PTFE medium,comprising a PTFE microporous membrane having secured directly to atleast one face thereof a PTFE web of microfibres). The PTFE-basedultra-sensitive sensors may be applied on an object or inside a vesselfor the purpose of detecting the presence of particular chemicalcompounds, such as ammonia in the liquid or vapor phase, in theenvironment to which the film is exposed.

Exemplary Preferred Embodiments

Exemplary embodiments of the present invention can be better understoodwith reference to FIGS. 1A-1D, and FIG. 2.

FIGS. 1A-D show exemplary embodiments of a combination pH and ammoniameasuring device for simultaneous, continuous measurement of solution pHand ammonia according to particular aspects of the present invention.FIGS. 1A, 1B, 1C and 1D show a combination sensor strip (submersiblemember having pH and ammonia-sensing means) as a standalone sensor strip(FIGS. 1A and 1D), and as reversibly attached to a sensor card(attachment base member) having integral or attached color charts (FIGS.1B and 1C).

FIG. 1C shows an attachment base member 12, having attached thereto asubmersible member 10. Alternatively, a plurality of proximatelyconnected, coordinately-submersible members, reversibly attachable tothe attachment base member 12, and suitable to be at least partiallysubmersible in a solution could be used. Also shown is at least onesubmersible ammonia-sensing portion 4 integral with or attached to thesubmersible member 10 or proximate submersible members, the at least oneammonia-sensing portion 4 having stable detection means (e.g.,immobilized dye) suitable to provide for a continuous visual indicatorof solution ammonia concentration. There is at least one submersiblepH-sensing portion 2 integral with or attached to the submersible member10 or proximate submersible members, the at least one pH-sensing portion2 having stable detection means (e.g., immobilized dye) suitable toprovide for a continuous visual indicator of solution pH. Additionallyshown is a visual ammonia indicator comparison means 8 (e.g., colorchart), attached to or integral with the attachment base member 12, andcomparable with the continuous visual indicator of the at least oneammonia-sensing portion 4 for standardized quantitative determination ofsolution ammonia concentration. There is also a visual pH indicatorcomparison means 6, (e.g., color chart), attached to or integral withthe attachment base member 12, and comparable with the continuous visualindicator of the at least one pH-sensing portion 2 for standardizedquantitative determination of solution pH. The dark area 14 in thisparticular exemplary embodiment corresponds to an aperture 14 throughthe submersible member 10, the aperture articulatible with a positioningmeans (not shown), such as a floatation member, or container attachmentmember (e.g., suction cup, etc.).

FIG. 2 shows, according to particular aspects of the present invention,the exemplary detachable combination pH and ammonia measuring deviceembodiment of FIG. 1D (standalone sensor strip), being used tocontinuously measure pH and ammonia in an aqueous environment (e.g.,aquarium, pool, hot tub, lake, river, pond, manufacturing container,etc.). The standalone sensor strip comprises a submersible member 10.Alternatively, a plurality of proximately connected,coordinately-submersible members could be used. The standalone sensorstrip additionally comprises at least one submersible ammonia-sensingportion 4 integral with or attached to the submersible member 10 orproximate submersible members, the at least one ammonia-sensing portion4 having stable detection means (e.g., immobilized dye) suitable toprovide for a continuous visual indicator of solution ammoniaconcentration. The standalone sensor strip further comprises at leastone submersible pH-sensing portion 2 integral with or attached to thesubmersible member 10 or proximate submersible members, the at least onepH-sensing portion 2 having stable detection means (e.g., immobilizeddye) suitable to provide for a continuous visual indicator of solutionpH. The dark area 14 in this particular exemplary embodiment correspondsto an aperture 14 through the submersible member 10, the aperturearticulatible with a positioning means (not shown), such as a floatationmember, or container attachment member (e.g., suction cup, etc.).

FIG. 3 shows, according to further aspects of the present invention,another exemplary combination pH and ammonia measuring deviceembodiment. The exemplary embodiment of FIG. 3, has two separablemembers: a submersible main body carrier or member 16 (in the instanceformed of a transparent plastic) comprising a reference color-chart 8included in a slot therein (or retaining means thereon), and an ammoniasensing portion 4 affixed to the outside of the carrier member 16; and apH sensing member 10 comprising a pH sensing portion 2. The color-chart8 within the main body carrier or member 16 is slidably removabletherefrom (e.g., for users not wanting to see anything more than thesensor in their aquarium). The pH sensing portion 2 on the pH sensingmember 10 inserts into, and/or appends from the main body carrier ormember 16. The pH sensing member 10 is easily removed and replaceable(e.g., as a replaceable cartridge), for example, in embodiments whereinthe service life of the pH sensing member 10 is not as great as that ofthe an ammonia sensing portion 4 affixed to the outside of the carriermember 16, and thus optimally is periodically changed without change ofthe main body carrier or member 16 comprising the ammonia sensingportion 4 affixed thereto. The exemplary pH indicator reference colorchart 6 is a continuous color gradient chart, starting at a positioncorresponding to clock position 9:00 and proceeding clockwise in thisinstance around to clock position 9:00. Likewise, the exemplary ammoniaindicator reference color chart 8 is a continuous color gradient chart,starting in this instance at a position corresponding to clock position3:00 and proceeding clockwise to clock position 9:00. The changes incolor gradient are illustratively indicated in the drawing by changingstippling patterns.

With respect to the exemplary inventive ammonia sensor of FIG. 3, userviewing is preferably by looking ‘front-on’ (e.g., perpendicularlyfacing the sensor). In alternate embodiments (FIG. 4), at least one ofthe ammonia sensing and/or pH sensing portions (e.g., sensor strips) issuitably configured (e.g., of sufficient length and structure) to extend(e.g., wrap, encircle, etc.) horizontally around, for example, the sidesof the main body member (e.g., or around the main body perimeter orportions thereof, regardless of the shape or configuration of theoverall main body) so that the at least one of the ammonia sensingand/or pH sensing portions can be seen from different angles (e.g., fromthe sides, back, etc.) by a user. The configuration of the sensor mainbody member, or of a side of the main body member can be flat, curved,raised concave, convex, etc. Such novel embodiments have severaladvantages not known in the respective art. For example, mounting ofsuch embodiments of the device on the side of an aquarium (e.g., thefrontal larger dimension of the sensor facing the side of the aquarium)not only provides for a front-on user view of the sensor from the sideof the aquarium different, but additionally provides a benefit that in auser view of this sensor from the front of the aquarium (e.g., a fullfrontal view of the aquarium, but only a side view of the sensor asso-disposed), the viewable side portion is relatively small (compared toa perpendicular view of the face of the sensor, or to prior art devices)and all that would be seen is a small piece (e.g., about ⅛″) of sensoron the edge of the device. Such an edge view, according to particularaspects of the present invention, is aesthetically very unobtrusive (notblocking viewing of the contents of the aquarium), but yet allowsviewing of a sufficient portion (e.g., about ⅛″), such that if thissensor edge view indicated that the aquarium conditions (e.g., pH and/orammonia concentration) were ‘off’ or problematic, the user could checkthe conditions more carefully by viewing the sensor face-on from theside of the tank. According to particular aspects, this is a substantialbenefit not provided in the prior art, which consists of products thatare planar, and can only be viewed frontally, such that in functionaloperation of such prior art sensor, all of the sensor area (e.g., allthe sensor material and color-indicator charting, etc) is viewable andis simultaneously obscuring the user view of the aquarium contents by anequivalent area.

According to various aspects, the objective of enabling sensor viewingof pH or ammonia sensor devices in generally, including art-recognizeddevices and those presently disclosed, from different user angles orpositions to reduce obscuring of the view of the aquarium contentsduring functional operation of the sensor, is accomplished in variousways, including but not limited to: wrapping the sensor partially orcompletely around, for example, a clear cylinder or tube; or using oneor more mirrors, lenses, or prism-like elements (e.g., plastic lenses orprism-like elements) to reflect a sensor image, or portion thereof, overa wider angle or dimension.

Additional Exemplary Embodiments

Particular aspects provide a combination pH and ammonia measuring devicefor simultaneous, continuous measurement of solution pH and ammonia,comprising: a submersible member, or a plurality of proximatelyconnected, coordinately-submersible members, suitable to be at leastpartially submersible in a solution; at least one submersibleammonia-sensing portion integral with or attached to the submersiblemember or proximate submersible members, the at least oneammonia-sensing portion having stable detection means suitable toprovide for a continuous visual indicator of solution ammoniaconcentration; at least one submersible pH-sensing portion integral withor attached to the submersible member or proximate submersible members,the at least one pH-sensing portion having stable detection meanssuitable to provide for a continuous visual indicator of solution pH; avisual ammonia indicator comparison means, comparable with thecontinuous visual indicator of the at least one ammonia-sensing portionfor standardized quantitative determination of solution ammoniaconcentration; and a visual pH indicator comparison means, comparablewith the continuous visual indicator of the at least one pH-sensingportion for standardized quantitative determination of solution pH.Preferably, the continuous visual indicator of the at least oneammonia-sensing portion comprises a colorimetric dye indicator.Preferably, the continuous visual indicator of the at least onepH-sensing portion comprises a colorimetric dye indicator.

In particular aspects, the visual ammonia indicator comparison meanscomprises an ammonia reference color indicator comparison chart integralwith or attached to the submersible member or proximate submersiblemembers. Alternatively, the ammonia reference color indicator comparisonchart is separate from, but movably comparable to the at least oneammonia-sensing portion of the submersible member or proximatesubmersible members. Preferably, the ammonia reference color indicatorcomparison chart comprises a color-gradient indicator comparison chart(e.g., a linear color-gradient chart, or a circular or wheelcolor-gradient chart).

In particular aspects, the visual pH indicator comparison meanscomprises a pH reference color indicator comparison chart integral withor attached to the submersible member or proximate submersible members.Alternatively, the pH reference color indicator comparison chart isseparate from, but movably comparable to the pH-sensing portion of thesubmersible member or proximate submersible members. Preferably, the pHreference color indicator comparison chart comprises a color-gradientindicator comparison chart (e.g., a linear color-gradient chart, or acircular or wheel color-gradient chart).

In particular embodiments, the combination pH and ammonia measuringdevice comprises an ammonia-sensing portion suitable to detect ammoniain the range of about 0.05 to about 0.5 ppm, about 0.05 to about 1.0ppm, about 0.005 to about 0.1 ppm, about 0.005 ppm to about 0.05 ppm,about 0.005 ppm to 0.05 ppm, about 0.005 to about 0.01 ppm, or about0.005 to 0.01 ppm. Preferably, the ammonia-sensing portion is suitableto detect ammonia in the range of about 0.005 to about 0.1 ppm. Inpreferred embodiments, the ammonia-sensing portion comprises abromophenol blue dye in a porous PTFE support.

In further aspects, the combination pH and ammonia measuring device,further comprises relational means for quantitatively determining totalammonia (NH₃ plus NH₄ ⁺), based on the visual indicator of solutionammonia concentration and the visual indicator of solution pH, incombination with the respective quantitative ammonia and pH comparisonmeans.

Yet further embodiments provide a combination pH and ammonia measuringdevice for simultaneous, continuous measurement of solution pH andammonia, comprising: an attachment base member; a submersible member, ora plurality of proximately connected, coordinately-submersible members,reversibly attachable to the attachment base member, and suitable to beat least partially submersible in a solution; at least one submersibleammonia-sensing portion integral with or attached to the submersiblemember or proximate submersible members, the at least oneammonia-sensing portion having stable detection means suitable toprovide for a continuous visual indicator of solution ammoniaconcentration; at least one submersible pH-sensing portion integral withor attached to the submersible member or proximate submersible members,the at least one pH-sensing portion having stable detection meanssuitable to provide for a continuous visual indicator of solution pH; avisual ammonia indicator comparison means, comparable with thecontinuous visual indicator of the at least one ammonia-sensing portionfor standardized quantitative determination of solution ammoniaconcentration; and a visual pH indicator comparison means, comparablewith the continuous visual indicator of the at least one pH-sensingportion for standardized quantitative determination of solution pH.Preferably, the continuous visual indicator of the ammonia-sensingportion comprises a colorimetric dye indicator. Preferably, thecontinuous visual indicator of the pH-sensing portion comprises acolorimetric dye indicator. In particular aspects, the visual ammoniaindicator comparison means comprises an ammonia reference colorindicator comparison chart integral with or attached to the attachmentbase member. Alternatively, the ammonia reference color indicatorcomparison chart is separate from the attachment base member, butmovably comparable to the at least one ammonia-sensing portion of thesubmersible member or proximate submersible members. Preferably, theammonia reference color indicator comparison chart comprises acolor-gradient indicator comparison chart (e.g., a linear color-gradientchart, or a circular or wheel color-gradient chart). In particularaspects, the visual pH indicator comparison means comprises a pHreference color indicator comparison chart integral with or attached tothe attachment base member. Alternatively, the pH reference colorindicator comparison chart is separate from the attachment base member,but movably comparable to the at least one ammonia-sensing portion ofthe submersible member or proximate submersible members. Preferably, thepH reference color indicator comparison chart comprises a color-gradientindicator comparison chart (e.g., a linear color-gradient chart, or acircular or wheel color-gradient chart). In particular embodiments, theammonia-sensing portion is suitable to detect ammonia in the range ofabout 0.05 to about 0.5 ppm, about 0.05 to about 1.0 ppm, or about 0.005to about 0.1 ppm. Preferably, the ammonia-sensing portion is suitable todetect ammonia in the range of about 0.005 to about 0.1 ppm. Inpreferred embodiments, the ammonia-sensing portion comprises abromophenol blue dye in a porous PTFE support. In certain aspects, theattachment base member is at least partially submersible in a solution,and the visual ammonia indicator comparison means and the visual pHindicator comparison means are integral with or attached to theattachment base member or to the submersible member or proximatesubmersible members. Preferred embodiments further comprise relationalmeans (charts, graphs, tables, etc.) to allow for quantitativedetermination of total ammonia (NH₃ plus NH₄ ⁺), based on the visualindicator of solution ammonia concentration and the visual indicator ofsolution pH, in combination with the respective quantitative ammonia andpH comparison means.

In yet further embodiments, at least one of the at least one submersibleammonia-sensing portion or the at least one submersible pH-sensingportion further comprises an antimicrobial agent. Exemplary candidateantimicrobial agents include silver, colloidal silver, silver dioxide,titanium dioxide, Triclosan to inhibit algae, or Thiabendazole-basedantimicrobials to inhibit fungi. Preferred are those agents that arestably associated with the submersible sensing portion(s). In certainembodiments the antimicrobial agent consists of a selectively porousbarrier material or membrane, or comprises a selectively porous barriermaterial or membrane, optionally in combination with one or moreantimicrobial agents such as those described herein. Preferably, atleast one of the at least one submersible ammonia-sensing portion or theat least one submersible pH-sensing portion further comprises anantimicrobial agent.

In preferred aspects, an AEM 5700 antimicrobial solution (e.g., a silaneQuaternary Ammonium Salt; namely, 3-(trimethoxysilyl) propyldimethyloctadecyl ammonium chloride); AEGIS ENVIRONMENTS, INC. Midland, Mich.),or the equivalent is used. In certain aspects, a pH sensor portionand/or an ammonia sensing portion is treated by brief immersion of theportion(s) in a solution of this product (e.g., 0.05% to about 10%(w/v)).

In further preferred aspects, the pH sensor and/or the ammonia sensor inenclosed (e.g., encased, sandwiched between, etc) by sealing it betweena transparent sheet (e.g., clear plastic sheet), which allows the sensorto be viewed, and a layer of a porous barrier material or membrane,filter, etc (e.g., porous barrier-filter membrane), wherein the porousbarrier material (e.g., membrane or filter) is suitable to precludemicrobes (e.g., bacteria,) from directly contacting the sensor andgrowing on or in it. In particular aspects, the antimicrobial agentconsists of such enclosing of the sensor(s). In additional embodiment,the antimicrobial agent comprises such enclosing of the sensor(s) incombination with one or more other antimicrobial agents (e.g., incombination with an AEM 5700 antimicrobial agent). For embodimentscomprising porous barrier material (e.g., membranes, filters, etc.), thebarrier material is preferably selected to have pores small enough tokeep, for example, bacteria from getting through to the sensor (e.g.,pores of 0.1 or 0.2 microns in diameter, or smaller), but having poreslarge enough to allow for passage of water and ions so that theunderlying sensor is exposed or bathed in water or solution and canrespond to the pH and/or ammonia changes in the solution (e.g., tankwater). In preferred aspects, the barrier membranes are hydrophilicpolymers that are wettable, and preferably robust and flexible for easyfabrication, and preferably not readily degraded by bacterial attack.Exemplary preferred barrier membranes include, but are not limited topolyether sulfone (e.g., Supor 100, with 0.1 micron pores (Pall); orsimilar products available from Millipore and Whatman), nylon,polycarbonate, etc, or combinations thereof. Additionally, aside fromthe microbial barrier property, particular barrier materialsadditionally have ‘intrinsic’ antimicrobial properties (e.g., chemicalproperties), or are processed to provide antimicrobial properties byinclusion/treatment with antimicrobial agents as described herein.Additionally, Glass (fibrous) or other porous materials such as aceramic that wet and will allow passage of water are encompassed by thepresent inventive methods. Membranes made with cellulosics are lesspreferred because bacteria can digest and eventually breach suchmembranes.)

Additional embodiments of the present invention provide a method fordetermining the total ammonia concentration in a solution, comprising:submersing, in a solution, a combination pH and ammonia measuring devicefor simultaneous, continuous quantitative measurement of solution pH andammonia; and quantitatively determining total ammonia (NH₃ plus NH₄ ⁺),based on a visual indicator of solution ammonia concentration and avisual indicator of solution pH. Preferably, the combination pH andammonia measuring device for simultaneous, continuous measurement ofsolution pH and ammonia are as described herein.

Yet further embodiments provide an ammonia detection device, comprisingporous matrix polytetrafluoroethylene (PTFE) having an ammonia-sensitiveimmobilized dye, the immobilized dye suitable to provide for acolorimetric determination of ammonia level, and wherein the detectiblerange of ammonia comprises a range of about 0.005 to about 0.1 ppm.Preferably, the ammonia-sensitive immobilized dye is BPB dye.Preferably, the porous matrix polytetrafluoroethylene (PTFE) comprises acomposite supported microporous PTFE medium, comprising a PTFEmicroporous membrane having secured directly to at least one facethereof a PTFE web of microfibres. Additional embodiments provide amethod for detecting ammonia in air, comprising exposing theabove-described ammonia detection device to air, wherein a colorimetricdetermination of air ammonia level is, at least in part, afforded.Particular aspects of this method comprise optical sensing tointerrogate the color of the ammonia-sensitive immobilized dye. Furtherembodiments provide a method for detecting ammonia in solution,comprising exposing the above-described ammonia detection device to atest solution, wherein a colorimetric determination of solution ammonialevel is, at least in part, afforded. Particular aspects of this methodcomprise optical sensing to interrogate the color of theammonia-sensitive immobilized dye.

Yet further methods comprise enhanced sensitivity sensors, comprisingporous matrix polytetrafluoroethylene (PTFE) having one or moreimmobilized indicator dyes to provide for an enhanced colorimetricdetermination of detected substance. In particular aspects, the porousmatrix polytetrafluoroethylene (PTFE) comprises a composite supportedmicroporous PTFE medium, comprising a PTFE microporous membrane havingsecured directly to at least one face thereof a PTFE web of microfibres.

Additional embodiments provide a combination pH and ammonia measuringdevice as otherwise described and disclosed herein, comprising aplurality of submersible ammonia-sensing portions, wherein at least twoof the ammonia sensing portions have different ammonia sensitivities. Incertain implementations, the at least two ammonia sensing portionshaving different ammonia sensitivities each have a different sensitivityrange selected from the ammonia sensitivity range group consisting ofabout 0.05 to about 0.5 ppm, about 0.05 to about 1.0 ppm, about 0.005 toabout 0.1 ppm, about 0.005 ppm to about 0.05 ppm, and about 0.005 ppm to0.05 ppm, about 0.005 ppm to about 0.01 ppm, or about 0.005 ppm to 0.01ppm. In certain embodiments, the ammonia measuring device comprises atleast three submersible ammonia-sensing portions each having a differentammonia sensitivity. In particular embodiments, the at least threeammonia sensing portions having different ammonia sensitivities eachhave a different sensitivity range selected from the ammonia sensitivityrange group consisting of about 0.05 to about 0.5 ppm, about 0.05 toabout 1.0 ppm, about 0.005 to about 0.1 ppm, about 0.005 ppm to about0.05 ppm, about 0.005 ppm to 0.05 ppm, about 0.005 ppm to about 0.01ppm, and 0.005 ppm to 0.01 ppm.

Yet additional embodiments provide a combination pH and ammoniameasuring device as otherwise disclosed and described herein, furthercomprising a temperature sensing portion (e.g., a liquid crystal-basedthermometer) to provide for readout of temperature.

Further aspects provide a combination pH and ammonia measuring device,comprising at least one main body member having face and side surfaces,the member comprising at least one ammonia sensing portion and at leastone pH sensing portion, wherein at least one of the ammonia sensing andpH sensing portions is suitably configured and disposed to extendsufficiently horizontally around at least one of the side surfaces ofthe main body, or a portion thereof, of the main body member sensor sothat a side view of at least one of the ammonia sensing and pH sensingportions by a user is operatively sufficient to provide at least one ofammonia and pH sensor input to the user. In particular embodiments, themain body member comprises a substantially rectangular or square planarplate having front and rear plate face surfaces defining a plate depth,and having side surfaces.

1. A method for determining the total ammonia concentration in asolution, comprising: submersing, in a solution, a combination pH andammonia measuring device having stable, spatially proximatecoordinately-submersible detection means suitable to provide for acontinuous visual indicator of pH and solution ammonia concentration forsimultaneous, continuous quantitative measurement of solution pH andammonia; and quantitatively determining total ammonia (NH₃ plus NH₄ ⁺),based on at least one visual indicator of solution ammonia concentrationand at least one visual indicator of solution pH, wherein a method fordetermining the total ammonia concentration in a solution is afforded.2. The method of claim 1, wherein the combination pH and ammoniameasuring device for simultaneous, continuous measurement of solution pHand ammonia comprises: a submersible member, or a plurality of spatiallyproximate, coordinately-submersible members, suitable to be at leastpartially submersible in a solution; at least one submersibleammonia-sensing portion integral with or attached to the submersiblemember or to one or more of the proximate submersible members, the atleast one ammonia-sensing portion having at least one stable detectionmeans suitable to provide for a continuous visual indicator of solutionammonia concentration; at least one submersible pH-sensing portionintegral with or attached to the submersible member or to one or more ofthe proximate submersible members, the at least one pH-sensing portionhaving at least one stable detection means suitable to provide for acontinuous visual indicator of solution pH; a visual ammonia indicatorcomparison component, comparable with the at least one continuous visualindicator of the at least one ammonia-sensing portion to provide forstandardized quantitative determination of solution ammoniaconcentration; and a visual pH indicator comparison component,comparable with the at least one continuous visual indicator of the atleast one pH-sensing portion for standardized quantitative determinationof solution pH, wherein the combination is suitable to provide forsimultaneous, continuous measurement of solution pH and ammonia.
 3. Themethod of claim 1, wherein the combination pH and ammonia measuringdevice for simultaneous, continuous measurement of solution pH andammonia comprises: an attachment base member; a submersible member, or aplurality of spatially proximate, coordinately-submersible members,reversibly attachable to the attachment base member, and suitable to beat least partially submersible in a solution; at least one submersibleammonia-sensing portion integral with or attached to the submersiblemember or to one or more of the proximate submersible members, the atleast one ammonia-sensing portion having at least one stable detectionmeans suitable to provide for a continuous visual indicator of solutionammonia concentration; at least one submersible pH-sensing portionintegral with or attached to the submersible member or to one or more ofthe proximate submersible members, the at least one pH-sensing portionhaving at least one stable detection means suitable to provide for acontinuous visual indicator of solution pH; a visual ammonia indicatorcomparison component, comparable with the at least one continuous visualindicator of the at least one ammonia-sensing portion to provide forstandardized quantitative determination of solution ammoniaconcentration; and a visual pH indicator comparison component,comparable with the at least one continuous visual indicator of the atleast one pH-sensing portion to provide for standardized quantitativedetermination of solution pH, wherein the combination is suitable toprovide for simultaneous, continuous measurement of solution pH andammonia.
 4. A method for detecting ammonia in air, comprising exposingan ammonia detection device to air, wherein the ammonia detection devicecomprises porous matrix polytetrafluoroethylene (PTFE) having anammonia-sensitive immobilized dye, the immobilized dye suitable toprovide for a colorimetric determination of ammonia level, and whereinthe detectible range of ammonia comprises a range of about 0.005 toabout 0.1 ppm, and wherein colorimetric determination of air ammonialevel is afforded.
 5. The method of claim 4, comprising optical sensingto interrogate the color of the ammonia-sensitive immobilized dye.
 6. Amethod for detecting ammonia in solution, comprising exposing an ammoniadetection device to a test solution, wherein the ammonia detectiondevice comprises porous matrix polytetrafluoroethylene (PTFE) having anammonia-sensitive immobilized dye, the immobilized dye suitable toprovide for a colorimetric determination of ammonia level, and whereinthe detectible range of ammonia comprises a range of about 0.005 toabout 0.1 ppm, and wherein a colorimetric determination of solutionammonia level is afforded.
 7. The method of claim 6, comprising opticalsensing to interrogate the color of the ammonia-sensitive immobilizeddye.
 8. The method of claim 4, wherein colorimetric determination ofammonia level is continuous and reversible within the detectible range.9. The method of claim 1, comprising use of a visual pH indicatorcomparison component and a visual ammonia indicator comparisoncomponent, comparable with the continuous visual indicators of pH andammonia, respectively, and relational means for quantitativelydetermining total ammonia (NH₃ plus NH₄ ⁺), based on the continuousvisual indicators of pH and ammonia, in combination with the respectivevisual pH and visual ammonia indicator comparison components.
 10. Themethod of claim 1, wherein the detectible range of ammonia comprises arange of about 0.005 to about 0.1 ppm.
 11. The method of claim 6,comprising use of a visual pH indicator comparison component and avisual ammonia indicator comparison component, comparable with thecontinuous visual indicators of pH and ammonia, respectively, andrelational means for quantitatively determining total ammonia (NH₃ plusNH₄ ⁺), based on the continuous visual indicators of pH and ammonia, incombination with the respective visual pH and visual ammonia indicatorcomparison components.